Regenerative frequency changer for multiplying and dividing



April 25, 1967 s. POLANIIECKI 3,316,478

REGENERATIVE FREQUENCY CHANGER FOR MULTIPLYING AND DIVIDING Filed Oct.23, 1963 INVENTOR. Salomon Pa/aniec/ri RIP wf k ATTORNEYS.

United States Patent REGENERATIVE FREQUENCY CHANGER FOR MULTIPLYING ANDDIVIDING Salomon Polaniecki, Cincinnati, Ohio, assignor to AvcoCorporation, Cincinnati, Ohio, a corporation of Delaware Filed Oct. 23,1963, Ser. No. 318,409

1 Claim. (Cl. 321-65) This invention relates to regenerative frequencychangers, and is useful both as a frequency divider and as a frequencymultiplier. v

An object of this invention is to provide a regenerative frequencychanger for multiplying or dividing an input frequency into one or moredifferent output wave frequencies.

Another object of this invention is to provide a regen erative frequencydivider or multiplier which includes means for regeneratively amplifyingthe generated harmonic.

A still further object of this invention is to provide a regenerativefrequency divider or multiplier which includes means for parametricallyamplifying the generated frequency.

A still further object of this invention is to provide voltageamplification of the multiplied frequency within the multipliercircuitry.

Generally, an input signal of one frequency is applied to an addernetwork in which a multiplicity of frequencies may already exist. Thefrequency of interest (a beat frequency) appears across the outputcircuit of a mixer and is then applied to an amplifier. The output ofthe amplifier is tuned to this particular frequency which is fed backfor reamplification to the input circuit through a unique feedbacknetwork including a multiplier. Invention resides in the uttersimplicity of the system for accomplishing improved results.

For a better understanding and for further objects of the invention,reference should now be made to the accompanying drawing in which thesingle figure illustrates one preferred embodiment of this invention.

The illustrated circuit is capable of deriving from an input signal i anamplified signal output at a frequency f /n. n may equal a Whole numberor fraction. The circuit uses an NPN-type transistor amplifier having abase 12, an emitter 14, and a collector 16. Base bias for the transistor10 is provided by means of a connection to the junction 18 ofseries-connected resistors 20 and 22 connected across a source of B+supply illustrated as a battery 24. The emitter 14 is connected to thegrounded side of the battery 24 through an emitter-resistor 26 bypassedfor alternating currents by means of a capacitor 28. The collector 16 isconnected to the other terminal of battery 24 through a resonant loadcircuit 30 comprising series-connected capacitors 32 and 34 connected inparallel with an inductor 36. The parameters of the resonant circuit 30are chosen for resonance at frequency Input signals at frequency f areapplied from a high impedance source 38 across a resonant circuit 39including a coupling capacitor 40 and an inductor 42 connected inparallel with a capacitor 44. The resonant circuit 39 is tuned to afrequency of f (n-1)/n. Signals developed across the resonant tankcircuit 39 are coupled to a diode 46 through a direct current blockingcapacitor 45. Forward bias for diode 46 is provided through a resistor47.

The semiconductor diode 46 is a non-linear device, and is incorporatedto serve as a mixer for the system. The application of two signals atfrequencies f and f (nl)/n yields the sum and difference frequencies,and in this case the difference frequency f /n is selected foramplification by the transistor 10. Selection is accomplished by use of3,316,478 7 Patented Apr. 25, 1967 an inductor 48 which is resonated bythe distributed capacitance of the inductor and of the circuit at f n.Capacitor 50 couples the voltage developed across the inductor 48 to thebase 12 of transistor 10. The resonant circuit 30 in the load circuit oftransistor 10 is also tuned to frequency f /n, and thus the outputselected at ter .minal 57 is comprised mainly of a signal at frequencyIn order to develop a voltage at frequency f /(n-1)/n for application tomixer diode 46, a unique regenerative feedback path is provided from thecollector 16 to the base 12 through a frequency multiplier comprising adirect current blocking capacitor 52 and a voltage-sensitive variablecapacitance diode 54. A resistor 56 connected between thevoltage-sensitive capacitance diode 54 and ground provides a runningback bias for the diode 54.

The application of fed back output voltages at frequency f /n to thevoltage-sensitive capacitor 54 causes the generation of a wide spectrumof harmonics. Since the resonant tank circuit 39 is tuned approximatelyto frequency f (n1)/n, substantially only that harmonic appears acrosstank circuit 39 for application to the mixer 46 along with the inputsignal at frequency f Since the inductor 48 is resonated at frequency f/n, this frequency is selected for reamplification in the transistor 10.

During the positive half cycle of the input signal at frequency f thediode 46 conducts and a signal is applied to the base 12, driving thetransistor 10 into 'proportionate conduction dependent upon theeffective direct voltage bias across the base-emitter junction. When thetransistor 10 conducts, a low impedance current path is establishedthrough the capacitor 50 and the base-emitter junction of transistor 10to produce an effective shunt across the resonant tank circuit 39. Thisshunt has the effect of loading the tank circuit 39, thereby loweringits Q and the voltage applied to the junction of diodes 46 and 54. Onthe negative half cycle the diode 46 cuts off, thereby cutting offconduction through the base-emitter junction of transistor 10 and henceremoving the shunt from the tank circuit 39. This has the effect ofrestoring the tank circuit Q to its initial value and hence the voltageapplied to the junction of diodes 54 and 46. Thus the diodes 46 and 54are pumped by the input signal, and therefore, in addition to thereamplification taking place in the transistor 10, the pumping of thevariable capacitance diode 54 results in the parametric amplification ofthe fed-back signals. Another important feature of this inventionresides in the fact that the diode 54 is voltage rather than currentdriven, and therefore the feedback loop requires very little power foreffective operation, and the efiiciency of the system is improved.

A frequency multiplier, in accordance with this inven tion, was reducedto practice using the following circuit parameters:

The input signal f =l mc.

The output signal f /n= I00 kc.

Resonant circuit 39, resonant at f (n-1)/n=900 kc. Resonant circuit 30,parallel resonant at f /n= kc.

Transistor 10 a Type 2N2651 Capacitors:

28 .,Ltf 4.7 40 pf 27 45 ,uf .01 50 ,uf 1 52 f" .0033 Resistors:

20 ohms 3.3K 22 do 1.8K 26 do 2.2K 56 do 100K 47 do 100K that thisinvention Diodes 46 1N645 (TI) 54 V-lSE (PSI) Inductor 48 mh 10 Theforegoing parameters were established to effect a frequency division inthe order of 10 to 1. Capacitor 52 has a relatively non-critical optimumvalue for each range of operation. Capacitor 50 functions primarily as adirect current block, and it should have a fairly low impedance withinthe r-ange of operation. The transistor 10 functions primarily as anamplifier of the generated frequencies. It simultaneously serves toamplify currents in the feedback loop. It is possible that the amplifiermay comprise a plurality of stages for some applications.

Various adaptations and modifications will at once become apparent topersons skilled in the art. For example, while in the specificembodiment as reduced to practice the resonant circuit 39 was tuned to f(nl)/n, in a different specific application it may be tuned to anyfrequency equal to f (nim)/n where m is any number other than n or zero,and the tank circuit 30 must be appropriately tuned to drive the desiredoutput frequency.

While a transistor was used and appears to be desirable for theparticular embodiment as reduced to practice, vacuum tubes maybesubstituted by changing the values of the bias network, i.e., resistors20 and 22. Furthermore, the amplifier might be an odd-number stagedirectcoupled system for high gain. It is intended, therefore, belimited only by the appended claim as interpreted in the light of theprior art.

I claim:

A frequency multiplier for multiplying an input frequency i to an outputfrequency f /n, where n is any number, comprising:

a high impedance source of input signals at frequency a first parallelresonant circuit connected across said source, said parallel resonantcircuit being tuned to a frequency f (nl)/n;

a non-linear semiconductor impedance device;

an amplifier comprising a transistor having base, emitter, and collectorelectrodes;

an input circuit for said amplifier, said input circuit comprising aninductor tuned to frequency f /n, said inductor being connected inseries with said nonlinear semiconductor impedance device across saidfirst parallel network, said inductor being connected across the baseand emitter electrodes of said transistor;

an output circuit for said amplifier, said output circuit comprising asecond parallel resonant circuit tuned to said output frequency mm;

a regenerative feedback path from said output circuit to said inputcircuit, said feedback path including a voltage sensitive variablecapacitance semiconductor device in series with said non-linearimpedance de vice and said inductor, said feedback circuit constitutinga series resonant network tuned broadly to said output frequency f /n;

and means for establishing a running direct voltage back bias on saidvoltage sensitive variable capacitance semiconductor device.

References Cited by the Examiner UNITED STATES PATENTS 2,816,220 12/1957Goodrich 307-885 2,991,359 7/1961 Danker 307-885 3,230,396 1/1966 Boelke307-885 JOHN F. COUCH, Primary Examiner. G. GOLDBERG, AssistantExaminer.

